Electron gun assembly



May 24, 1960 o. M. HUETER, JR

ELECTRON GUN ASSEMBLY 2 Sheets-Sheet 1 Filed Dec. 16, 1958 INVENTOR. J n BY M4, l f /w I Mm nLEcTRoN GUN ASSEMBLY Oscar M. Hueter, in, Santa Cruz, Califi, assig'nor to gtewart Engineering Company, a corporation of Caliornia Fiied Dec. 16, 1958, Ser. No. 780,694

15 Ciaims. (Cl. 313-69) This invention relates to an electron gun assembly and in particular to an electron gun assembly for use in a travelling wave tube.

In travelling wave tubes, a tubular beam of electrons is passed coaxially through a helix structure. To obtain proper interaction between the electrons in the beam and magnetic field in the helix structure, a high degree of accuracy in concentricity and spacing of the electron beam relative to the helix structure is necessary. To permit mass production of such travelling wave tubes, it is further necessary to provide means for producing such accurately arranged electron beams which are economical of construction and readily assemblable by persons of ordinary skill.

The principal feature of this invention is the provision of a new and improved electron gun assembly.

Another feature is the provision of an electron gun assembly for use in a travelling wave tube, comprising a new and improved arrangement of insulator and electrode elements.

A further feature is the provision of such an electron gun assembly wherein the electrode elements are provided with flange means for co-operation with adjacent annular insulator elements to effect an automatic coaxial alignment of the electrode and insulator elements.

A still further feature is the provision of such an electron gun assembly having new and improved means for longitudinally aligning the beam-forming annular orifices of a succession of such electrodes.

A yet further feature of the invention is the provision of such an electron gun assembly having new and improved means for permitting gas flow therethrough.

Yet another feature is the provision of such an electron gun assembly having new and improved means for associating a tubular cathode element with an aperture of an end one of such electrodes.

Still another feature is the provision of such an electron gun assembly having new and improved means for securing the elements thereof.

Other features and advantages of the invention will be apparent from the following description, taken in connection with the accompanying drawing wherein:

Fig. l is an enlarged fragmentary diametric section of an electron gun assembly embodying the invention;

Fig. 2 is a transverse section taken approximately along the line 22 of Fig. 1;

Fig. 3 is an exploded view thereof, the cathode element being shown fragmentarily;

Fig. 4 is an enlarged fragmentary diametric section of a modified electron gun assembly embodying the invention;

Fig. 5 is a transverse section thereof taken approximately along the line 5-5 of Fig. 4; and

Fig. 6 is an exploded view of the modified form of an electron gun assembly, the cathode element being shown fragmentarily.

In the exemplary embodiment of the invention, as disclosed in Figs. 1 through 3 of the drawing, an electron States Patent 0 gun assembly is shown to comprise a stacked array of annular insulators 10 and beam-forming electrodes 11. At one end of the assembly is coaxially disposed a cathode 12 and a cathode heat shield 13. From the cathode, electrons pass through aligned apertures in the assembly of electrodes and insulators wherein they are formed into an accurately arranged beam having a predetermined transverse cross section which is delivered through a snout 14 adapted to be secured in accurate coaxial relationship with a travelling wave tube helix (not shown). Herein the electron beam is shown as tubular.

More specifically, insulators 10 comprise annular ceramic or metallic elements. To provide improved accuracy, insulators 10 are accurately ground to the desired dimensions and concentricity.

The beam-forming electrodes 11 are formed of suitable metal, such as sheet stainless steel, tantalum or molybdenum, permitting them to be quickly and accurately formed as by punching in a suitable press (not shown). Each electrode comprises a flat plate or formed portion 15 provided with an aperture 16 in the mid-portion thereof. The aperture comprises a discontinuous annular orifice arranged concentrically of the central axis of the electrode, the annular orifice being divided into a plurality of equiangular portions by intermediate radially extending elements 17 formed integrally in the plate portion. Extending radially outwardly from plate portion 15 is a plurality of arms 18 terminating in right-angularly turned fingers 19. The fingers 19 are turned alternately in opposite directions and are accurately spaced from the electrode axis so as to engage successively alternately the outer surface 20 of oppositely adjacent insulators 10. Thus, an accurate coaxial alignment of the insulators and electrodes is obtained. In the illustrated embodiment, the electrode 11a adjacent cathode 12 engages only one insulator, every other one of the fingers 19 extending freely longitudinally outwardly in the direction of the cathode. The electrode 11b adjacent snout 14 engages an insulator '10 on one side thereof and a snout centering ring 21 on the other side thereof fixedly secured to one end of snout 14. The outer surface 22 of ring 21 is accurately congruent with outer surfaces 20 of the insulators and, therefore, electrode 11b accurately coaxially aligns snout 14 with the electrode and insulator assembly.

Intermediate each pair of arms 18, the periphery 23 of the electrode plate portions 15 is extended radially inward to have a minimum radial dimension from the axis of the electrode less than the radius of the inner surface 24 of insulators 10. Herein, peripheral portions 23 of the electrode plate portions 15 are arcuately concave and continue into arms 18 substantially adjacent fingers 19 thereof. Thus, a plurality of exhaust outlet openings 25 is formed, permitting rapid exhausting of undesirable gases which may form in the electron gun assembly during pumping and'use. Three additional exhaust outlets are provided in snout 14 in the form of openings 26 through the wall thereof adjacent ring 21, and a similar additional exhaust outlet is provided in the cathode heat shield 13 in the form of an opening 27 through the wall thereof. To facilitate longitudinal alignment of apertures 16, elements 17 are similarly angularly spaced in each electrode. Further, the angular spacing of arms 18 and the angular relationship of the arms 18 to the elements 17 are made similar in each electrode. Thus, an automatic alignment of the elements 17 of the apertures of each of the electrodes is effected merely by stacking alternately a plate and insulator which are aligned by arms 18 during assembly of the electron gun.

To facilitate the securing of cathode 12 in coaxial alignment with insulators 10, the cathode size is accurately correlated with that of aperture 16 of electrode 11a.

In addition, the intermediate elements 17a of electrode 11a are ofiset longitudinally toward snout 14 to permit end 12a of the cathode to be partially received within the aperture. An accurate coaxial disposition of'heat shield 13 relative to electrode 11a is efiected by means of three ofiset tabs 28 on electrode 11a over which tabs one end 13a of the cathode heat shield is snap fitted. Heat shield 13 is then permanently secured to electrode 11a by suitable means such as brazing, as desired.

The insulators and electrodes are maintained in tight stacked relationship by means of a plurality of spring clips 29, herein three such clips are provided. Each spring clip is provided at one end with a hook 30 which loops about an outwardly turned finger 19 of the electrode 11a. At the opposite end, the spring clip is provided with a reversely turned arm 31 which engages an annular insulator 32 movably received on snout 14 and abutting centering ring 21. As best seen in Fig. 1, snout insulator 32 may be provided with a suitable recess 33 for improved retention therein of spring clip arm 31.

In assembling the electron gun of the instant invention, the heat shield and electrode 11a are first secured and the cathode inserted and welded in place. This subassembly is then held in a suitable jig (not shown) to permit proper stacking of insulators and electrodes 11 thereon. In the illustrated embodiment, three electrodes are provided, it being obvious that any desired variation in the number of electrodes in the electron gun assembly may be obtained by providing a suitable corresponding member of electrodes and insulators. When the last electrode has been placed on the stack, the snout 14 with external centering ring 21 is installed thereon and snout insulator 32 positioned against the centering ring. The spring clips 29 are then installed, as with tweezers, to draw the elements into tight stacked relationship. This simple assembly may be performed by persons having only ordinary skill, and yet the resultant stacked assembly is one having a high degree of accuracy suitable for providing a highly accurate tubular electron beam.

Referring now to Figs. 4 through 6, a modified form of electron gun assembly, generally designated 200, is shown to comprise a stacked array of annular insulators 110 and beam-forming electrodes 111. The electrodes 111 are generally similar to electrodes 11 of electron gun assembly 100, except that the arms 18 are omitted and the plate portion 115 of the electrodes 111 extends outwardly to define a circle having a diameter substantially equal to the outer diameter of the insulators 110. Plate portion 115 is provided with a plurality of annularly spaced openings 123 concentrically outward of the beamforming aperture 116 in the mid-portion of the plate portion 115. Each electrode is provided with a plurality of turned fingers 119 similar to fingers 19 of electron gun assembly 100. The disposition of openings 123 is correlated with the arangement of fingers 119 so that when the fingers of the respective electrodes are longitudinally aligned, the openings 123 are correspondingly longitudinally aligned to provide a plurality of gas exhaust passages extending longitudinally through electron gun assembly 200.

Electron gun assembly 200 further differs from electron gun assembly 100 in the provision of means for bonding the insulators to each adjacent electrode for retaining the insulators and electrodes in the desired stacked relationship. More specifically, each of insulators 110 is provided with a layer of brazing metal 133 on its opposite end surfaces. Thus, when the insulators and electrodes are assembled, as seen in Fig. 4, they may be retained in the assembled relationship by applying sufiicient heat to the metal 133 to braze the insulators to the electrodes. Thus, the spring clips 29 of electron gun assembly 100 are eliminated in assembly 200, while yet a securely maintained assembly of the elements of the electron gun assembly is effected. Further, the cathode heat shield 113 and the snout 1 14 may be dimensionally coordinated with the insulators and electrodes to provide a substantially continuous cylindrical periphery of the electron gun assembly 200 with fingers 119 projecting only slightly therefrom and serving as readily available means for making electrical connections to the individual electrodes.

Otherwise than noted above, electron gun assembly 200 is substantially similar in structure and functioning to electron gun assembly previously described.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the con struction and arrangement may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. An electron gun assembly comprising: a pair of coaxially juxtaposed annular insulators; and an electrode having a plate portion between and extending transversely of said insulators and provided with an aperture in the mid-portion thereof, and a plurality of turned fingers successively alternately engaging the periphery of both insulators to maintain coaxial alignment of said aperture and said insulators.

2. An electron gun assembly comprising: an annular insulator; and a pair of electrodes each having a plate portion, said plate portions extending transversely across opposite ends of said insulator, each of said electrodes being further provided with an annular aperture in the mid-portion thereof and a plurality of arms terminating in turned fingers at least one of which is turned in one direction from the flat plane of the plate portion and at least one of which is turned in the opposite direction there from and positionally related to said apertures to engage the periphery of the insulator to maintain coaxial alignment of said apertures with said insulator and the apertures of the other electrode.

3. The electron gun assembly of claim 2 wherein the arms of each plate portion are similarly angularly spaced and the electrodes are arranged with their arms longitudinally aligned.

4. The electron gun assembly of claim 2 wherein the apertures of each of said plates are similarly discontinuous and the plates are arranged to have their discontinuities longitudinally aligned and wherein the arms of each plate are similarly angularly spaced and the electrodes are arranged to have their arms longitudinally aligned, the disposition of said arms relative to the arrangement of said apertures being similarly correlated in each of said electrodes whereby said apertures are automatically aligned when said arms are aligned.

5. An electron gun assembly comprising: an annular insulator; an electrode having a plate portion extending transversely across one end of said insulator and provided with an aperture in the mid-portion thereof, said aperture comprising an annular orifice divided into a plurality of portions by a plurality of radially extending elements offset longitudinally rearwardly of the front fiat plane of the plate portion, said electrode further having a plurality of turned fingers engaging the periphery of the insulator to maintain coaxial alignment of said aperture with said insulator; and a cathode cylinder having one end received in said annular orifice to extend through the front fiat plane of the plate portion.

6. An electron gun assembly comprising: a plurality of annular insulators; and a plurality of electrodes each having a plate portion provided with an aperture in the midportion thereof, and a plurality of turned fingers, said insulators and electrodes being stacked in alternate coaxial succession, a number of said fingers of each electrode being oppositely extending whereby the fingers of intermediate electrodes engage longitudinally extending portions of each of oppositely adjacent insulators.

7. The electron gun assembly of claim 6 wherein a spring is extended between an insulator at one end of the assembly and an electrode at the opposite end of the assembly to maintain the insulators and electrodes in tight stacked relationship.

8. The electron gun assembly of claim 7 wherein the spring is provided with a hook looped about one of the fingers of the electrode at said opposite end.

9. The electron gun assembly of claim 6 wherein said insulator at an end of the assembly is provided with a recess and said spring is provided with a turned arm engaging said insulator in said recess.

10. An electron gun assembly comprising: a plurality of annular insulators; a plurality of electrodes each having a plate portion provided with an aperture in the midportion thereof, and a plurality of turned fingers, said insulators and electrodes being stacked in alternate coaxial succession, said fingers of each electrode being successively alternately oppositely extending whereby the fingers of intermediate electrodes engage each of oppositely adjacent insulators; and means bonding the insulators to each adjacent electrode for retaining the insulators and electrodes in stacked relationship.

11. An electron gun assembly comprising: a plurality of annular insulators; and a plurality of electrodes each having a plate portion provided with an aperture in the mid-portion thereof and a plurality of annularly spaced openings concentrically outward of said aperture, and a plurality of turned fingers, said insulators and electrodes being stacked in alternate coaxial succession, said fingers of each electrode being successively alternately oppositely extending whereby the fingers of intermediate electrodes engage each of oppositely adjacent insulators, and said openings of each electrode being longitudinally aligned with corresponding openings of the other electrodes.

12. An electron gun assembly comprising: a pair of coaxially juxtaposed annular insulators; and an electrode having a plate portion between and extending transversely of said insulators and provided with an aperture in the mid-portion thereof, and a plurality of turned fingers, at least one of which engages the periphery of one insulator and at least one of which is oppositely turned and engages the periphery of the other insulator to maintain coaxial alignment of said aperture and said insulators.

13. The electron gun assembly of claim 12 wherein said plate portion is provided with a plurality of radially extending arms terminating in said turned fingers, the periphery of the plate portion between said arms having a minimum radial dimension less than the inner radius of the insulator thereby to provide a gas discharge path through the assembly and spaced substantially from the axis thereof.

14. The electron gun assembly of claim 12 including at least three turned fingers engaging said one insulator and three oppositely turned fingers engaging said other insulator.

15. The electron gun assembly of claim 2 wherein the periphery of the plate portion between said arms has a. minimum radial dimension less than the inner radius of the insulator thereby to provide a gas discharge path leading outwardly from the assembly and spaced substantially from the axis thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,310,811 Schantl et al Feb. 9, 1943 2,441,792 Brian May 18, 1945 2,376,439 Machlett May 22, 1945 2,463,635 McIntosh Mar. 8, 1949 2,553,580 Haas May 22, 1951 2,722,625 Bingeman Nov. 1, 1955 2,740,067 Sorg Mar. 27, 1956 2,748,307 Hickey May 29, 1956 2,802,133 Haas Aug. 6, 1957 2,844,759 Bryan July 22, 1958 

